Specificity Is an Important Characteristic of Intercellular Communication; Which of These

Specificity is an important characteristic of intercellular communication; which of these best explains how it occurs?

A) The phospholipid composition of the plasma membrane differs among cells.
B) Protein receptors are only located on the surface of target cells.
C) All cells have the same DNA, so any cell can express protein receptors for a specific chemical.
D) Chemical messengers are all proteins, so bind only to receptors that are proteins.
E) Protein receptors for chemical messengers are only expressed in specific target cells.